The Amateur Amateur: Assaulting the Battery II

By Gary Hoffman, KB0H
Contributing Editor
February 12, 2002

Last time on The Amateur Amateur: I described how the battery for my hand-held stopped holding a full charge, vented my frustrations regarding a battery seller, and went on to discuss my dubious attempts to revive my failing battery.

I had zapped and frozen my ailing NiCad battery pack and gotten nowhere. I didn't even know if the so-called "whiskers" said to form inside NiCad cells--and which I was trying to destroy--were real or just in the mind of a chemist who had inhaled too many fumes. All I knew was that if the battery hadn't been dead before, I surely must have killed it. I decided to perform an autopsy.

Battery cases are not really designed to be opened, so my battery dissection was not particularly neat. Once inside, I found 10 cells--individual 1.2-V NiCads--of about the same diameter and half the length of regular AA cells. I found a local vendor who sold replacements and bought 10 of them. I then carefully measured the charge of each of the old cells (yes, I actually know how to operate a voltmeter) and determined that two of them were in bad shape. I removed the two bad cells, replaced them with new cells, closed up the case and everything worked perfectly. Yeah, right.

battery and cells

Battery and battery-ettes--the cells found inside.

You know me better than that. Of course that's not what happened. Everything was true up until "I removed the two bad cells . . ." The cells were linked in series by what appeared to be metal tape. I tried peeling off the tape. Nope. It wasn't held on with glue. I tried unsoldering it. That didn't work either. I examined the cells and "tape" under a magnifying glass and found tiny little marks indicating the tape had been sort-of riveted to the cells. I busted a lot of "rivets" and tore up much of the tape, but did manage to extract the two bad cells. I soldered in two new ones and closed up the case.

Before I could attach the repaired battery to a charger, I noticed it was getting warm. No, hot. Very hot. I suddenly felt like I was in a World War II movie holding a live grenade in my hands. I resisted a strong impulse to throw the battery through the nearest window then drop to the floor and cover my head. Instead, I quickly disassembled the battery and yanked out the collection of cells. It only took a moment to find the short circuit. I carefully reassembled the package and closed the case. It stayed cool this time.

I charged up the repaired battery. After one day's use, it still acted as if two cells were bad. I disassembled it again. I checked each cell again. There were two bad cells--two of the older cells that had checked out okay the first time. I replaced them.

The same thing happened the next day. And the day after that. I felt like I was in some sort of time warp in which the same events repeated themselves day after day (remember that movie, Groundhog Day?). Every time I replaced two cells, two more of the original cells would die. Each time I broke the "riveted" tape, things got messier. And for some reason, each time I opened the battery case, it was harder to close.

I gave up the idea of replacing cells. It just wasn't working. Replacing all of the cells with new ones cost about the same as just buying a new battery. I decided that doing the latter was easier and safer.

But why had my battery died in the first place?

battery charging station

Battery charging station: Check the oil, wash the windshield, and charge s-l-o-w-l-y.

I heard a lot about something called the "memory effect." This is, by far, the most talked-about "problem" with NiCad batteries. I did a little research into it and found a vast amount of conflicting information. Some people described the phenomenon in great detail. Others said that the memory effect existed only in certain NiCads, and definitely not the ones in popular use. Yet others insisted that the memory effect was nothing more than an urban legend. Egad! Who was an amateur amateur to believe!?

I was not a battery scientist. I didn't know which "expert" to believe. I knew, for sure though, that the memory effect was not what ailed my battery. The reason my battery failed was that the fast charger had cooked it. Literally.

Fast chargers pump electrical energy into the batteries at such a high rate that the batteries heat up. The heat eventually causes a chemical breakdown. Many battery vendors do not mention this when you buy a fast battery charger. They will sell you batteries, then sell you the means to destroy them, apparently so that you will have to buy more.

There is another well-known battery vendor that sells nickel metal hydride (NiMH) batteries. If you browse this vendor's Web site and look very carefully, you will find a very small message telling you that the vendor recommends using only slow chargers on NiMH batteries. It seems that fast chargers can cause NiMH batteries to explode. The vendor sells a special fast charger that apparently shuts itself off when the battery gets hot (notice that I didn't say if the battery gets hot, but when the battery gets hot). I guess it's more like putting it in a crock pot than putting it in a microwave oven.

I kept checking the Internet, but cold-fusion batteries hadn't hit the market yet. Since it looked like I was stuck with NiCad and NiMH batteries for a while, here's what I did.

battery burial

Dead but still deadly. Dispose of carefully. Visit the RBRC Web site for more information.

First: I threw away my fast charger and bought three battery packs. I rotate these in service. When battery A is in the radio, battery B is a backup and battery C is in the slow charger. At the end of the day I simply put A in the charger, B in the radio, and C is the new backup. None of them gets cooked, stewed, or nuked.

Second: I received a lot of advice on the proper way to "zap" NiCads back to life. Except for one hellishly dangerous recommendation (use a stun gun), all of the suggested techniques required much more time, equipment, and effort than I'm willing to invest. Although I'm taking the easy route (just buy a new battery), I do wish to thank everyone who wrote to me.

Third: Even dead NiCads are dangerous. I was considering having a nice, quiet burial ceremony at a toxic waste dump. Before I actually did that, however, I found information on how to recycle them on the Missouri Household Hazardous Waste. (Your state's recommendations and regulations may vary.) The Rechargeable Battery Recycling Corp is a nonprofit organization that provides recycling assistance in the US.

Do I have any final advice? Yes. If it takes a hacksaw to open something, there's probably a reason for it, and it's best left alone.

For additional information, see "Honey, They've Shrunk the Batteries!" by Ken Stuart, W3VVN, in December 2001.

Editor's note: ARRL member Gary Hoffman, KB0H, lives in Florissant, Missouri. He's been a ham since 1995. Hoffman says his column's name-- "The Amateur Amateur"--suggests the explorations of a rank amateur, not those of an experienced or knowledgeable ham. His wife, Nancy, is N0NJ. Hoffman has a ham-related Web page. Readers are invited to contact the author via e-mail, [email protected].

© 2002 American Radio Relay League


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